Polikarpov I-3

The Polikarpov I-3 was the first of Nikolai Polikarpov's fighter designs to enter front line service, and was the first of a long line of designs that reached their peak with the I-153.

The first of Polikarpov's biplanes to take to the air had been the two-seat 2I-1N. This was an impressively streamlined aircraft built around a wooden semi-monocoque fuselage, constructed out of layers of laminated wood. Tragically the only prototype crashed on 31 March 1926 when the surface of the upper right wing pealed off. Both of the crewmen were killed, and a prolonged investigation into the cause of the accident delayed work on Polikarpov's next aircraft, meaning that it eventually emerged after Sukhov's I-4/ ANT-5.

When work did begin the first problem was the lack of a suitably powerful Soviet aircraft engine. Two imported engines were considered - the Wright Tornado III radial engine and the BMW VI liquid cooled inline engine. At first the Tornado was chosen, but Polikarpov felt that it wasn't powerful enough, and the BMW was soon adopted.

A wooden mock-up of the new design was ready by April 1927, and the design was approved in principle on 14 May. Formal approval from the Commissariat of the Air Force followed on 3 June, and work on a full size model began. In October static tests began using this model, while work began on the first of two prototypes. The first prototype made its maiden flight on 21 February 1928, and tests lasted into April. The second prototype followed in August 1928.

The design of the I-3 borrowed heavily from that of the 2I-N1, although most structural elements were made stronger (and thus heavier) in response to the fatal crash that had destroyed the earlier aircraft. The semi-monocoque fuselage was made of layers of veneered wood glued together, while the wings had box-type plywood spars and were covered with plywood and fabric.

Just under 400 I-3s were built, starting in 1928. The peak of production came in 1930 when 250 aircraft were built, and production ended in 1931. The first 39 were powered by imported BMW engines, while the rest got Soviet licence-built 680hp M-17 engines. The prototypes and first 75 production aircraft were armed with two Vickers machine guns, which were then replaced with 7.62mm PV-1 machine guns.

The I-3 entered service in 1929, replacing the Grigorovich I-2 in units based in Belorussia. The aircraft was used by squadrons based at Smolensk, Bryansk, Kiev and Bobruisk, as well as at training schools. The number of aircraft in service peaked at 297 at the start of 1932, before falling as the I-3 was replaced by the I-5, I-15 family and I-16 monoplanes. As was common with fighter pilots of the early 1930s Soviet fighter pilots preferred manoeuvrability to speed, and so the I-3 was never as popular as the newer Polikarpov aircraft that replaced it.